Wafer side edge cleaning apparatus

ABSTRACT

A wafer side edge cleaning apparatus includes: a cleaning device including a fixing element and a wafer brush disposed beneath the fixing element. The wafer brush is in the shape of a frustum. The frustum has a tapered surface contacting with a side edge of a wafer. The top surface of the frustum is larger than the bottom surface of the frustum. When cleaning the side edge of the wafer, the wafer and the wafer brush are rotated in different directions and a cleaning solution flows out from the fixing element rinses and washes the side edge brush.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a wafer cleaning apparatus, and moreparticularly, to an apparatus for cleaning the side edge of a wafer.

2. Description of the Prior Art

Semiconductor chip fabrication is a complicated process that involvesmany manufacturing steps. These steps may include layering, patterning,etching, doping, chemical mechanical polishing (CMP), etc. It is wellknown that, during the various steps in these operations, the surfaces,or side edges of the semiconductor wafers will become contaminated withresidues. In particular, the side edge of the wafer may suffer frompeelings.

The removal of these contaminants and peelings is a priority tosemiconductor chip fabricators because contaminants and peelings willpollute the chamber and influence the quality of the integrated circuiton the wafer.

Conventionally, one system used to remove wafer contaminants on thesurface is a wafer cleaning device. In the wafer cleaning device, asemiconductor wafer is held to a stage. The stage has a vacuum suctionmember to suck the back side of the wafer, so the wafer can be disposedon the stage stably. Then, the wafer is rotated and the surface of thewafer is scrubbed by a brush.

Although a conventional wafer cleaning device can effectively clean thefront side of the wafer, such systems fail to provide a cleaning methodat the side edge/bevel area to remove contamination and peelings.

SUMMARY OF THE INVENTION

It is therefore one objective of the present invention to provide anapparatus that cleans the side edge of wafers, including the bevel area(when present).

According to a preferred embodiment of the present invention, a waferside edge cleaning apparatus includes: a wafer stage for holding androtating a wafer, wherein the wafer has a side edge, and a cleaningelement includes: a fixing element, and a wafer brush fixed onto thefixing element, the wafer brush having a tapered surface contacting theside edge of the wafer. The tapered surface defines a bottom surface anda top surface of the wafer brush; the bottom surface is away from thefixing element, the top surface contacts the fixing element, and thebottom surface is smaller than the top surface. A cleaning solutionrinses the wafer brush when the side edge of the wafer is subject tocleaning by the wafer brush.

According to a preferred embodiment of the present invention, thetapered surface and the top surface define an included angle which isbetween 45 and 80 degrees.

According to another preferred embodiment of the present invention, thewafer side edge cleaning apparatus further includes a bolt disposedunder the fixing element and penetrating the wafer brush, and a nutdisposed under the wafer brush and screwed on the bolt to fix the waferbrush on the fixing element.

According to another preferred embodiment of the present invention, theside edge of the wafer comprises a bevel.

From one aspect, the features of the present invention are that the sideedge of the wafer is cleaned by the tapered surface of the wafer brush.Because the tapered surface contacts the side edge of the wafer, thecontainments or peelings on the side edge can be adsorbed on the waferbrush so these containments or peelings can be removed.

These and other objectives of the present invention will no doubt becomeobvious to those of ordinary skill in the art after reading thefollowing detailed description of the preferred embodiment that isillustrated in the various figures and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 depicts a wafer side edge cleaning apparatus schematically.

FIG. 2 depicts a three-dimensional graph of a cleaning elementschematically according to a first preferred embodiment of the presentinvention.

FIG. 3 depicts a sectional view of the cleaning element shown in FIG. 2along the line AA′.

FIG. 4 depicts a sectional view of the cleaning element shown in FIG. 2along the line BB′.

FIG. 5 depicts a three-dimensional graph of a cleaning elementschematically according to a second preferred embodiment of the presentinvention.

DETAILED DESCRIPTION

FIG. 1 depicts a wafer side edge cleaning apparatus schematically. Asshown in FIG. 1, the wafer side edge cleaning apparatus includes a waferstage 12 for holding and rotating a wafer 14. The wafer 14 includes aside edge 16, and the side edge 16 includes a bevel 17. A vacuum suctionmember (not shown) sucks the wafer 14 by a suction force F₁ to fix thewafer on the wafer stage 12. The side edge of the wafer is cleaned afterthe steps of layering, patterning, etching, doping, or chemicalmechanical polishing, and before the succeeding fabrication step.Furthermore, when the side edge 16 is subject to cleaning, the bevel 17of the side edge 16 is cleaned as well.

When the side edge 16 is subject to cleaning, the wafer 14 is rotated toa first direction: for example, the wafer 14 is rotated clockwise. Atthis point, a controlling arm 18 moves a cleaning element 20 downward,and a wafer brush 22 of the cleaning element 20 is therefore disposed ata side of the side edge 16 in a horizontal direction. Then, thecontrolling arm 18 moves the cleaning device 20 toward the side edge 16of the wafer in a horizontal direction, and a tapered surface 24 of thewafer brush 22 contacts the side edge 16 of the wafer 14. At this point,the wafer brush 22 has a lateral force F₂ and a downward force F₃ withrespect to the wafer 14. According to a preferred embodiment of thepresent invention, the suction force F₁ should be greater than thedownward force F₃ provided by the wafer brush 22, otherwise one point onthe rim of the wafer 14 will be raised upwards, making the wafer 14 actlike a seesaw. The lateral force F2 should be equal to a coefficient offriction μ multiplied by the suction force F₁; that is, F₂=F₁×μ. Thecoefficient of friction μ represents the coefficient of friction of thewafer 14 on the stage 12. In this way, the wafer 14 can be fixed on thestage 12 stably without moving in a lateral direction. Moreover, duringthe process of the side edge 16 of the wafer being cleaned, the waferbrush 22 is rotated to a second direction: for example, the wafer brush22 can be rotated counterclockwise.

FIG. 2 depicts a three-dimensional graph of a cleaning elementschematically according to a first preferred embodiment of the presentinvention. FIG. 3 depicts a sectional view of the cleaning element inFIG. 2 along the line AA'. FIG. 4 depicts a sectional view of thecleaning element in FIG. 2 along the line BB'.

As shown in FIG. 2, the cleaning element 20 further includes a fixingelement 26 having a bolt 30 attached under the fixing element 26. Thewafer brush 22 is fixed under the fixing element 26 with the bolt 30penetrating through the wafer brush 22. A nut 32 is disposed beneath thewafer brush 22 and screws on the bolt 30 to fix the wafer brush 22securely. The wafer brush 22 has to be replaced by a new oneperiodically so as to maintain the best cleaning result. The nut 32 canbe easily taken apart from the bolt 30, therefore, the wafer brush 22can be changed simply. Maintenance work of the wafer brush 22 becomessimple. Furthermore, because the nut 32 can change its position bymoving up or down, the combination of the bolt 30 and nut 32 for fixingthe wafer brush 22 with different sizes and shapes has also been takeninto consideration. Therefore, based on different requirements, thewafer brush 22 with different sizes or shapes can be fixed on the fixingelement 26 by adjusting the position of the nut 32.

It should be noted that the wafer brush 22 is preferably in the shape ofa frustum. The wafer brush has a tapered surface 24, and the taperedsurface 24 defines a bottom surface 34 and a top surface 36 of the waferbrush 22. The bottom surface 34 is away from the fixing element 26, andthe top surface 36 contacts the fixing element 26. Moreover, the bottomsurface 34 is smaller than the top surface 36. Referring to FIG. 3,according to a preferred embodiment of the present invention, thetapered surface 34 and the top surface 36 of the wafer brush 22 definean included angle θ which is between 30 and 90 degrees, and preferablybetween 45 and 80 degrees so as to clean the side edge 16 entirely.Furthermore, the wafer brush 22 can be made of materials which have lesshardness than the wafer, and have the properties of high adhesivenessand stability, such as resin. Preferably, the wafer brush 22 is formedby poly vinyl alcohol (PVA), because PVA has excellent plasticity,emulsifying, and adhesive properties. It is also resistant to oil,grease and solvent. Therefore, PVA is suitable for forming the waferbrush 22 which has a special profile. Moreover, the wafer brush 22 madeof PVA will not be consumed by the cleaning solution 28 because of itsresistivity to solvent.

As illustrated in FIG. 2 and FIG. 4, at least an opening 38 is formed onthe fixing element 26. A cleaning solution supplying tube (not shown)for supplying the cleaning solution 28 can be set within the fixingelement 26. The exit of the cleaning solution supplying tube can bepositioned at the opening 38, and the cleaning solution 28 can flow outfrom the opening 38. The cleaning solution 28 can be de-ionized waferincluding conductive ions. The conductive ions may be formed by carbondioxide dissolved in the de-ionized wafer.

Please refer to FIG. 1 and FIG. 4. When the side edge 16 including thebevel 17 is subjected to cleaning, the cleaning solution 28 flows outfrom the opening 38 and rinses the wafer brush 22. The wafer brush 22becomes moist and elastic after the cleaning solution 28 flows onto thewafer brush 22. Therefore, contaminants on the side edge 16 can beeasily absorbed on the wafer brush 22 and the wafer 14 will not bedamaged because the hardness of the wafer brush 22 is less than that ofthe wafer 14. Moreover, the cleaning solution 28 not only can rinse thewafer brush 22, but also can wash down the containments adsorbed on thewafer brush 22. Therefore, when the cleaning element 20 is used forcleaning the side edge 16 of the wafer, the cleaning solution 28 flowingout from the fixing element 26 will wash the wafer brush 22 at the sametime. The cleaning solution 28 flows out from the wafer brush 22continuously during the cleaning of the side edge 16. Moreover, becausethe fixing element 26 is disposed above the wafer brush 22, the cleaningsolution 28 flows from the upper part of the wafer brush 22 to the lowerpart of the wafer brush 22. In this way, the tapered surface 24 can beentirely washed and rinsed by the cleaning solution 28. The containmentsor peelings on the tapered surface 24 can be removed sufficiently, andthe wafer brush 22 can absorb sufficient cleaning solution 28. Inaddition, because the wafer brush 22 has a bottom surface 34 smallerthan the top surface 36, the containments or peelings on the taperedsurface 24 can flow downward along the profile of the tapered surface 24smoothly, and the containments or peelings will not get stuck on thewafer brush 22 or the nut 32. Furthermore, when the side edge 16 isbeing cleaned, the bottom surface 34 is substantially parallel to thefront side or the back side of the wafer 14.

FIG. 5 depicts a three-dimensional graph of a cleaning elementschematically according to a second preferred embodiment of the presentinvention, wherein like numerals designate like components in thedrawing.

The difference between the cleaning element in FIG. 5 and in FIG. 2 isthat the opening 38 is set on the side wall of the fixing element 26 inFIG. 5, and the opening 38 is set within the fixing element 26 in FIG.2. Moreover, the cleaning solution supplying tube for providing cleaningliquid is not limited to be set inside the fixing element 26. Forinstance, the cleaning solution supplying tube can be set on a holder(not shown) positioned near the wafer brush 22, and the cleaningsolution flowing from the cleaning solution supplying tube can therebyrinse the wafer brush 22.

The fixing element of the present invention has openings so that thecleaning solution can flow out from the openings to rinse the waferbrush, and the tapered surface of the wafer brush contacting the sideedge of the wafer can adsorb containments or peelings on the side edge.Furthermore, the cleaning solution can wash down the containments orpeelings adsorbed on the wafer brush.

Those skilled in the art will readily observe that numerousmodifications and alterations of the device and method may be made whileretaining the teachings of the invention.

1. A wafer side edge cleaning apparatus comprising: a wafer stage forholding and rotating a wafer, wherein the wafer has a side edge; and acleaning element comprising: a fixing element; and a wafer brush fixedonto the fixing element, wherein the wafer brush has a tapered surfacecontacting the side edge of the wafer, the tapered surface defines abottom surface and a top surface of the wafer brush, the bottom surfaceis away from the fixing element, the top surface contacts the fixingelement, and the bottom surface is smaller than the top surface, andwherein a cleaning solution rinses the wafer brush when the side edge ofthe wafer is subject to cleaning by the wafer brush.
 2. The wafer sideedge cleaning apparatus of claim 1, wherein the tapered surface and thetop surface define an included angle between 30 and 90 degrees.
 3. Thewafer side edge cleaning apparatus of claim 2, wherein the includedangle is between 45 and 80 degrees.
 4. The wafer side edge cleaningapparatus of claim 1, wherein the fixing element comprises at least oneopening and the cleaning solution flows out from the opening.
 5. Thewafer side edge cleaning apparatus of claim 1, wherein the cleaningsolution comprises de-ionized water.
 6. The wafer side edge cleaningapparatus of claim 5, wherein the cleaning solution comprises conductiveions.
 7. The wafer side edge cleaning apparatus of claim 1, wherein thewafer brush comprises resin.
 8. The wafer side edge cleaning apparatusof claim 7, wherein the wafer brush comprises poly vinyl alcohol (PVA).9. The wafer side edge cleaning apparatus of claim 1, wherein when theside edge of the wafer is subject to cleaning, the wafer is rotated to afirst direction, and the wafer brush is rotated to a second direction sothat contaminants on the side edge can be adsorbed on the wafer brush.10. The wafer side edge cleaning apparatus of claim 1, furthercomprising a bolt disposed under the fixing element and penetrating thewafer brush, and a nut disposed under the wafer brush and screwed on thebolt to fix the wafer brush on the fixing element.
 11. The wafer sideedge cleaning apparatus of claim 1, wherein the side edge of the wafercomprises a bevel.